In Duncan v. Louisiana, the U.S. Supreme Court ruled in 1968 that states must provide a trial by jury in serious criminal cases. The case arose when Gary Duncan, a black teenager from Louisiana, was convicted of simple battery - an offense punishable by up to two years imprisonment without the option for a jury trial under state law. Duncan appealed his conviction arguing it violated his Sixth Amendment right to a jury trial as applied to the states through the Fourteenth Amendment's Due Process Clause. In its decision, with Justice Byron White writing for majority (7-2), the court held that while not every criminal prosecution requires a full-fledged jury trial and some petty crimes or minor offenses may be exempted; any crime carrying potential sentence of six months or longer is sufficiently "serious" to require provision of constitutional right for jury trials.

In the dissenting opinion for Duncan v. Louisiana, Justice John Marshall Harlan II argued that the majority's decision to incorporate the Sixth Amendment right to a jury trial in state criminal proceedings was an overreach of judicial power. He contended that this ruling disregarded long-standing principles of federalism by imposing a uniform standard on states' legal systems without sufficient constitutional basis. Instead, he believed it should be left up to individual states to decide whether or not they wanted to provide jury trials for certain types of crimes based on their own unique circumstances and traditions. Furthermore, he expressed concern about potential negative consequences from extending this right too broadly, such as increased costs and delays in administering justice at the state level.